1. Field of the Invention
The present invention relates to dispersants, which have been phosphorylated and/or boronated, useful as thermal stability additives in distillate fuels. Subjecting distillate fuels to thermal stress tends to result in significant deposit formation in the fuel and exhaust systems. It is highly desirable and an object of this invention to reduce the deposit formation in thermally stressed distillate fuels, such as jet fuel and diesel fuel. This goal is obtained by formulating distillate fuel compositions containing phosphorylated and/or boronated dispersants which are the reaction products of i) at least one phosphorus compound and/or a boron compound and ii) at least one ashless dispersant.
2. Background Discussion
Phosphorylated, boronated dispersants within the scope of the present invention are known and disclosed in U.S. Pat. No. 4,857,214 (Papay et al.) for use as antiwear additives for lubricants. The No. 4,857,214 patent does not disclose that these dispersants are useful in fuel compositions or suggest that these additives would be effective at reducing deposit formation in thermally stressed distillate fuels. Most particularly, the No. 4,857,214 patent does not relate to fuel compositions or teach the use of phosphorylated, boronated dispersants in distillate fuels.
U.S. Pat. No. 5,505,868 (Ryan et al.) discloses dispersants formed by reacting ashless dispersants, with at least one dibasic acylating agent, a phosphorus compound and a boron compound. The No. 5,505,868 patent further mentions that the dispersants can be used as detergents or deposit reducers in hydrocarbonaceous fuels.
In U.S. Pat. No. 5,139,643 (Roling et al.) phosphorus derivatives of polyalkenylsuccinimides as antifoulants in liquid hydrocarbonaceous mediums, such as crude oil, are disclosed. The reference does not teach the use of phosphorylated polyalkenylsuccinimides in distillate fuel compositions.
U.S. Pat. No. 4,855,074 (Papay et al.) discloses products formed from a long chain succinimide and a benzotriazole which are optionally boronated. These products are formed by reaction in the presence of an amine or an organic phosphorus compound. The use of these dispersants in fuels is mentioned.
European Patent No. 0,678,568 discloses methods and compositions for reducing fouling deposit formation in jet engines. The methods employ a derivative of (thio)phosphonic acid added to the turbine combustion fuel.